The utility of buttressing an endoscopic mechanical stapler with strips of bovine pericardium in resection of pulmonary bullous areas was evaluated by comparing the duration of air leakage in two randomized patient groups, one with and one without buttressing. The duration of air leakage was not related to bulla size in either group but showed a linear relation with the radiologic emphysema score in both groups (p < 0.001) and was shorter when the stapler had been fitted with bovine pericardium, but significantly reduced (p = 0.019) only in patients with a high emphysema score. The duration of air leakage was thus related to emphysema score, and in patients with high scores was shortened by application of bovine pericardium to the stapler.